J. Pharmacol. Exp. Ther., vol.199, p171 (1976) proposes a synthesis of an anti-cocaine antibody for use in an immunoassay for cocaine, and an antigen necessary in preparing the antibody. The antibody reported is, however, a polyclonal antibody which can be obtained from refined blood of a goat or rabbit immunized using an antigen of ecgonine of Formula (1). ##STR1##
To obtain an anti-cocaine antibody highly specific for cocaine, a cocaine-protein conjugate must be formed by using a derivative keeping the cocaine framework as precise as possible. Unfortunately, ecgonine lacks a methoxycarbonyl group and benzoyl group each characteristic of the cocaine molecule.
The polyclonal antibodies of the prior art can simply be prepared; on the other hand, it is less reproducible because the properties of the prodluct depend on individual experimental animals. Thus, it is quite difficult to provide antibodies of the same quality.
Polyclonal antibodies are a mixture of a diversity of antibodies having respective affinities. All the affinities they have prevent the use of a polyclonal antibody in a sensitive detection system because of their low affinity for the molecule of interest. In accordance with the above, we tried to obtain a monoclonal antibody having high affinity for cocaine; however, we could not succeed because ecognine as an antigen is too different in structure from cocaine.